Gamma ray detectors are commonly used in nuclear and high-energy physics research, medical imaging, diffraction, nondestructive testing, nuclear treaty verification and safeguards, and geological exploration. Polycrystalline scintillators useful for gamma ray detectors typically have a high light output, high stopping efficiency, fast response, good proportionality, and minimal afterglow. More importantly, polycrystalline scintillators can be processed using conventional ceramic processing methods to achieve large sizes with low cost and high production rate.